Hardware-wise and internal-design-wise I prefer the Xbox Series X. The system is a teeny bit more powerful than PS5 but basically almost exactly the same. The differences between the two are extremely negligible. Of course Microsoft's system fully conforms to the DirectX 12.2 ("DX12 Ultimate") spec. Also the Xbox consoles have way better support for VRR, and they also support 1440p. XBSX I guess has a more boring external visual design, but PS5 is too garish and weird-lookin' for me (and it is also way too dang large). However the whole point of buying a system is for the exclusive games available only on that system. That's one of the main reasons PS4 came out on top during 8th-gen. Microsoft doesn't really have any hard-hitting exclusives, but on the plus side, everything they got comes out on PC, so there's no need to even buy their console hardware to begin with. Although with more and more Sony IPs hitting PC, I hoping this generation there won't be a need to buy the PS5 either.
I have no idea which one of the two systems is easier to find these days. I think maybe XBSX? I've heard of more instances of people being able to walk into stores and find one, whereas people still have to bust their @sses off trying to get their hands on a PS5. That said, most of my friends who were in the market for a 9th-gen system have a PS5. I do have 3 friends with an XBSX, but one of those also has a PS5. One of those friends was able to just walk into a store and buy his XBSX. The other ordered it off of Microsoft's website with virtually no issues.